WASHINGTON—A California state senator has introduced a bill that would create severe restrictions on the use of zinc or zinc oxide in tires.

Zinc oxide producers, however, say the bill is based on faulty premises and unrealistic projections of zinc levels in California state waterways.

Sen. Ben Allen, D-Santa Monica, introduced California Senate Bill 1260 on Feb. 18. As of now, SB 1260 is short on details that will be filled in later. For example, it would ban the sale of motor vehicle tires in California that contained more than a yet-to-be-specified amount of zinc by weight, after Jan. 1 of a year to be specified during consideration of the legislation.

The bill would require tire makers to screen potential alternatives to zinc as an additive in tires, but also would allow them to apply to the California Department of Toxic Substances Control to delay the prohibition on zinc as to certain applications for tires. Manufacturers who violated the ban would face unspecified civil penalties.

SB 1260 is the first legislation of its type in the world, according to an aide to Allen. However, a fact sheet from Allen's office on SB 1260 states the Netherlands has subsidized research into lower zinc levels in tire formulations. As the fact sheet notes, zinc is used in tire manufacturing as a catalyst in the curing process to increase durability.

“As the tread gradually wears away with use, zinc-laden rubber debris is left on roadways and gets washed into the storm sewer systems, polluting nearby rivers, lakes and coastal areas,” the fact sheet says.

The document quotes the California Stormwater Quality Association (CASQA) as saying that almost every zinc emission inventory identifies tire wear as a major source of zinc in urban runoff. However, zinc oxide producers disagree.

California has identified 49 sites where it says zinc levels exceed what is deemed safe, said Eric Van Genderen, manager of environment and sustainability at the International Zinc Association.

But of those 49, nine are sedimentary, according to Van Genderen. “If you take those sedimentary sites, it's more of a legacy issue, and you can't link the zinc sediment to current use,” he said.

The remaining 40 sites are aquatic, involving rivers, streams, lakes and other bodies of water in motion stretched over nine of the state water boards in California, Van Genderen said. If tires are the main source of zinc pollution, that would imply that population density would be a factor in zinc levels. But existing evidence doesn't support that conclusion, he said.

“Sen. Allen is in Los Angeles County, and the water board for that county has identified high levels of zinc,” he said. “But the highest levels are in the Central Valley, which has 7 million inhabitants at most, spread over a large area. “I don't like to point figures at others, but it's not difficult to assume that there are feedlots and fertilizer plants there that may also be sources of zinc.”

The water board in the San Francisco Bay area, meanwhile, has found no sites with elevated zinc levels, according to Van Genderen. “To conclude that population density is in any way linked to elevated zinc concentrations is unfounded,” he said.

The latest CASQA report, reviewing the literature on zinc, concluded that tires are a source of zinc pollution, Van Genderen said. At the same time, however, CASQA did not demonstrate that leachability of zinc from tires is possible.

“CASQA acknowledged the evidence against tires is circumstantial,” he said.

Zinc is used in so many applications, including detergents and cosmetics, that it is difficult to identify any single source of zinc pollution, according to Van Genderen. “In Germany, 80 percent of the zinc problem comes from legacy mining,” he said. “But it's difficult to find deep pockets to go after in that case.”

Next steps

The search for alternatives to zinc oxide in tires has been going on for many years, for various reasons, Van Genderen said.

One alternative is lead oxide, which obviously is unacceptable, he said. Calcium oxide and magnesium oxide are also alternatives, but are more effective for rubbers such as latex.

Van Genderen said the IZA has had a meeting with Allen's office and coordinated activities with the Rubber Manufacturers Association. An RMA spokesman said the association has relayed its concerns about the bill to Allen.

“We'll be working to educate other California legislators on this issue and believe that the bill will attract opposition from other groups,” the RMA spokesman said.

The California Senate Committee on Environmental Quality has scheduled an April 6 hearing on SB 1260, said the spokeswoman for Allen. If it passes, the bill will advance to the Judiciary Committee, which has until April 22 to consider it.

Tire and rubber product manufacturing is the single largest market for zinc oxide. Stefan Schlag of IHS Chemicals said at the recent Zinc Oxide Conference that global demand for zinc oxide in 2015 was 1.5 million metric tons, of which 830,000 tons came from the rubber industry.

ที่มา : www.rubbernews.com